There could be other fingerprints besides MAC addresses.

How about my smartwatch, or my $29 earbuds? They are always conveniently near the 'random mac' and can be used to fingerprint.

don't bring them to a protest, simple :)

Yeah, not sure many people are aware their beloved tech is spying on them. At this point face recognition and other tech can make it such that everyone is traced, filed and automatically sent summons of some sort.